Coordination polymerization of olefinically unsaturated monomers is well known and has led to the great proliferation of elastomeric and plastic compositions of matter, such as polyethylene, polypropylene, and ethylene propylene rubber. Early pioneers utilized catalysts with such activators as aluminum alkyls and later development extended this work to bulky ligand-containing (e.g., .eta..sup.5 -cyclopentadienyl) transition metals ("transition metal compounds") with activators such as alkyl alumoxanes. The most recent developments have shown the effectiveness of ionic catalysts comprised of transition metal compound cations activated by noncoordinatinig anions. See for example EP-A-277 004 and U.S. Pat. No. 5,198,401, both of which are fully incorporated by reference. These references describe protonation of transition metal compounds by anion precursors to form stable ionic catalysts.
U.S. Pat. No. 5,427,991 describes the chemical bonding of noncoordinating anionic activators to supports so as to prepare polyanionic activators that when used with the transition metal compound, avoids the problem of catalyst desorption experienced when ionic catalysts physically adsorbed on inert supports are utilized in solution or slurry polymerization. The supports are inert monomeric, oligomeric, polymeric or metal oxide supports which have been prepared so as to incorporate chemically bound, noncoordinating anions.
There is a need to address further both the preparation of supported ionic catalyst systems, and a need to find supported metallocene catalysts that do not adversely affect the polymer product. Substituted, bridged indenyl transition metal compounds, supported on silica or polymer supports, have long been observed to produce polypropylenes with more regio defects and subsequently shorter meso run lengths as determined by .sup.13 C NMR compared to the propylene polymers produced by the respective unsupported transition metal compounds in solution. These defects result in a decrease in the polymer melting point which is undesirable for many applications. This invention solves this long-standing problem by minimizing or even eliminating these defects through manipulation of the activator to transition metal ratio.